The present invention relates to an information recording-reproducing apparatus for recording and reproducing digital and analog information including video and audio information for video and audio equipment and external memory units of electronic computers.
External memory units for information equipment including electronic computers are roughly divided into disk-type and tape-type apparatuses. For all the disk-type information recording-reproducing apparatuses and a part of the tape-type information recording-reproducing apparatuses, the surface of the recording media is split into tracks in which information is recorded.
The recording and reproducing operation for each track requires the movement of a head providing recording-reproducing means on the track. This operation is called the tracking. The tracking is generally performed on the basis of the signal reproduced from reproducing means. In order to improve the recording density, the track width and the space between tracks have been reduced. In parallel with this, efforts have been made to improve the absolute mechanical accuracy of apparatuses for securing an accurate tracking.
In magnetic disks, for recording binary-coded digital signals, codes are converted (modulated) in such a way that the signal obtained at the time of reproducing is capable of self synchronization. These methods, some of which are for recording the FM (frequency modulation) signals, are strictly aimed at recovering clock signals required for deciding on the code from the reproduction signal.